Assessing cardiovascular and vertebral/hip fracture risk and bone condition using quantitative computed tomography and/or dual energy x-ray absorptiometry

ABSTRACT

Methods and systems for computer assisted detection of arterial calcification, for example in the abdominal artery, by using measurements such as those conventionally taken with a dual x-ray energy bone densitometers at single energy or dual energy, or by a CT/QCT device for a localization of scout view, and for using the calcification assessment either alone or with other information to assess and report a risk of a cardiovascular event, alone or together with other information such as BMD and vertebral fracture risk.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of parent application Ser.No. 11/542,280 filed Oct. 2, 2006, which is hereby incorporated byreference.

FIELD AND BACKGROUND

This patent specification is in the field of methods and equipment forassisting medical professionals in assessing a patient's cardiovascularand vertebral/hip fracture risk and bone condition parameters such asbone mineral density (BMD) using x-ray measurements derived fromlocalization or scout scans taken with a computed tomography (CT) or aquantitative computed tomography (QCT) device and/or scans taken with adual energy x-ray absorptiometry (DXA) device. In addition, thisapplication pertains to assessing patient risks by using x-raymeasurements of other anatomy.

QCT has long been used to estimate BMD. Typically, the patient ispositioned on the patient bed of a CT scanner together with a QCTphantom that is in the field of view and has known characteristics. Alateral CT localization or scout scan is taken to identify vertebrae andperhaps to adjust CT gantry angle tilt to place one or more axial CTslices through the center or another selected plane of one or moreselected vertebrae. The CT slice images that include the phantom andvertebral bodies such as L1 and L2, or T1 through L3, are processed toderive an estimate of the patient's BMD. This and other approaches tomeasuring bone mass are discussed in a 1989 paper by Christopher E.Cann.²⁸ (The superscript numerals refer to the documents cited at theend of the detailed description; all of those documents, as well as thepatents and patent applications cited in this patent specification, arehereby incorporated by reference herein.) QCT products are commerciallyoffered in this country by a number of companies, including MindwaysSoftware, Inc. of Baltimore, Md. and Image Analysis, Inc. of Columbia,Ky.^(29,30) See, also, U.S. Pat. No. 4,233,507 and FDA 510(k) documentK031991 dated Jul. 30, 2003 regarding a product of Image Analysis, Inc.named DXAVIE Hip and Spine.³¹ While the lateral localization or scoutscan typically taken for a QCT procedure may allow visualization ofvertebral fractures and of aortic calcifications, as mentioned inmaterial published by Image Analysis, Inc.³⁰, it is believed that thereis no teaching or suggestion of using such CT or QCT lateral scans toquantify vertebral fracture assessment or aortic calcification in anautomated manner.

A different modality, dual x-ray energy bone densitometry (DXA), haslong been used mainly to obtain bone condition assessment information,including the projected bone mineral density (BMD, in g/cm²) at variousanatomical sites. One example of DXA systems is available from Hologic,Inc. of Bedford Mass. under the trade name Discovery. It has anexamination table and a C-Arm at opposite ends of which are mounted anx-ray tube and a multi-detector array. The patient is positioned on theexamination table between the x-ray tube and the detector array of theC-arm. For the assessment of bone mineral density, the x-ray detectorand a fan-shaped beam of x-rays from the tube are scanned as a unitaxially along the patient, while the x-rays are alternatively switchedbetween high and low energy ranges. By comparing the relativeattenuation of the x-rays at the two energies, the contributions toattenuation due to the soft tissue can be subtracted. In otherequipment, dual energy x-ray measurements are obtained by using a steadyx-ray beam of relatively broad energy range impinging on detectors thatmeasure respective energy ranges of the beam, or on a detector that candiscriminate between energy ranges, such that high and low energyseparation is done by the detector. At least in principle, similarresults may be obtained without scanning, using an x-ray beam of asufficient cross-section and a 2D array of detector elements. In eachcase, an image can be obtained of the bony structure of the body by thesoft-tissue subtraction method. This image is then input into BMDanalysis, which calculates and reports the BMD. The image can bedisplayed by showing it on a screen and/or printing it and can be storesin PACS or other storage/retrieval systems together with otherdensitometry and patient data.

When the patient's spine is scanned with a DXA device, the displayedimage is similar to that in conventional spine radiography except thatit requires less x-ray exposure and the entire spine or any desired partthereof can be scanned in one pass and shown as a single image. Theimage also is similar to a localization or scout scan image taken with aCT or QCT device. In DXA, the image can be derived from measurements atboth x-ray energy ranges or at one of them (single energy image). In thecase of systems such as the Discovery, a single energy image can beobtained by selecting a fixed, relatively narrow energy range ratherthan alternating between two energy ranges. If a dual energy image isalready available but a single energy image is desirable for furtherprocessing or another purpose, it can be extracted simply by using onlythe x-ray detector outputs for one of the energies or by adding the twoenergies together rather than subtracting them. In systems that use thedetector to separate high and low x-ray energy, a single energy imagecan be extracted by using only the output of only one of the detectorsets or at one of the narrower energy ranges, or by adding the high andlow x-ray energies together rather than subtracting them.

The options for densitometers offered by Hologic, Inc. include CADfx,which carries out computer processing of the spinal image to help detectvertebral fractures in DXA images, and Instant Vertebral Assessment(IVA), sometimes referred to as vertebral fracture assessment (VFA),wherein vertebral deformities can be evaluated similar to standardradiograph or CT image reading methods. IVA images are lateral spineimages typically taken at single energy. While the images produced usingDXA IVA are not of sufficient quality for general radiological use, ithas been observed that the quality of IVA images is similar to that ofabdominal radiographs for visualizing abdominal aorta calcifications(AAC). In fact, AAC can be seen in DXA images sufficiently well to haveallowed the Food and Drug Administration (FDA) to clear Hologic, Inc.(510K clearance K060111 approval Apr. 24, 2006) for visualizing AAC withits DXA equipment.

The abdominal aorta is a large, fluid filled vessel comprised of softtissue. It can be barely visible on conventional x-ray images and istypically is visualized with the use of a radio-opaque contrastmaterial. A vessel that is calcified usually presents with a linear oreggshell calcified pattern which is typical of calcification in the wallof a fluid filled structure. The history of using radiographs toidentify abdominal aortic calcifications iswell-established.^(1,2,5,11,14,15,16) A recent (2005) review article ofmethods for detection of abdominal aortic calcifications describes threeprimary methods: plain radiograph, ECT, and CT. It concludes, “Presentlyno modality has been accepted as the gold standard for the measurementof abdominal aortic calcification,”⁵ but observes that “The simplestmethod of detecting abdominal aortic calcification is with plainabdominal X-ray.”⁵

Abdominal Aortic Calcification (AAC) is seen anterior to the lumbarspine in lateral view and is graded in severity by several methods⁸⁻¹⁰related to the length of the AAC seen in the image. The publishedliterature indicates a graded association between the length of the AACseen in the image and the risk of future morbidity andmortality.^(1, 3, 6, 7) In a typical grading scheme, the posterior andanterior walls of the aorta are graded in the area in front of the L1-L4vertebra for total length of calcifications seen. For example, 0, ≦1 cm,1 to 2.4 cm, 2.5 to 4.9 cm, ≧5 cm is considered, absent, dubious, mild,moderate, and severe, respectively.¹⁰ It has been reported that AAC isdiagnostic for arteriosclerosis¹⁻⁴. AAC is believed to be stronglyassociated with a number of diseases, independent of traditionalclinical risk factors such as age, cigarette use, diabetes mellitus,systolic blood pressure, left ventricular hypertrophy, body mass index,cholesterol, and HDL cholesterol.^(1, 3, 5-7) The known literatureidentifies plain radiography, CT and ECT as the modalities to be usedfor AAC detection and quantification. Published patent application US2003/0176780 A1 discusses detection and quantification of aorticcalcium, but from CT slice images rather than lateral localization ofscout images. MRI is also referenced as a modality in connection withassessing atherosclerosis.²³

SUMMARY OF DISCLOSURE

The systems and method disclosed in this patent specification generallyrelate to assessing patient risk of cardiovascular and vertebral/hipfracture by computer-processing x-ray measurements typically taken ingenerally lateral views with a CT or QCT scanner and/or similar viewstaken with a DXA device, and estimating bone condition parameters suchas BMD by computer-processing x-ray measurements taken in generallyaxial views with a QCT scanner or lateral view in a DXA scan, andreporting various combination of assessments and estimates inparticularly useful ways. If a localization of scout scan of the spineis used, preferably it is over a greater number of vertebrae thancommonly used for QCT procedures, for example, it encompasses T2 throughL5, although a scan over more or less vertebrae or over a different spanof the spine can be used as well. Preferably, vertebral fractureassessment is done using information from a generally laterallocalization or scout scan with the QCT scanner, but in the alternativecould be done using similar information from a scout scan with anotherCT scanner or from a single or dual energy lateral scan with a DXAdevice, or with information from another modality. Also preferably, boneparameters such as BMD can be derived from the axial scans of a QCTprocedure, but could alternatively be derived from a DXA procedure orfrom another modality. AAC can be assessed from the x-ray measurementtaken in the course of the lateral localization or scout CT scan or froma single energy or dual energy lateral scan with a DXA instrument. Witha DXA device, a single energy image can be obtained in much shorter timeand at lower x-ray dose, while a dual energy image can require higherdose and longer acquisition time but lessen some effects of soft tissue.For example a densitometer such as the Discovery can acquire a singleenergy lateral image of vertebrae T4 to L4 in about 10 seconds but cantake several times that for a similar dual energy image. Dual energyimages can be used instead if the longer scan time and higher dose arejustified or already available, as in the case of DXA devices that use awide energy range in the x-ray beam and separate the two energies at thedetector system. It should be understood that the term single energy isused in this patent specification to refer to an x-ray energy rangerather than to a single value of the energy spectrum, and the term dualenergy refers to two ranges of x-ray energy ranges that may partlyoverlap.

Instead of or in addition to estimating bone parameters such as BMD fromQCT or DXA measurements of the spine, similar measurements can be takenof other anatomy, such as of the hip using known technology and methods.In addition, structural analysis of the hip can be carried out asdiscussed, for example, in patent application PCT/US 06/43730, and theresults can be included in a report that also reports other parameters.

A non-limiting example of a method disclosed in this patent (1)estimates vertebral fracture risk from a lateral CT localization orscout scan of several vertebrae, such as T2-L5 or another span of thepatient's spine, and/or of the hip, (2) estimates the risk of acardiovascular event using aortic calcification information obtainedfrom the same lateral CT scan, and (3) estimates a bone parameter suchas BMD from a QCT procedure that involved one or more vertebrae and/orthe hip. As is typical in QCT procedures, first a lateral localizationor scout scan is taken with the CT instrument. This scan typically is atlower x-ray dose than a conventional chest or abdomen 2D x-ray image,but its quality is sufficient for vertebral fracture risk assessment andAAC analysis. For example, whereas a conventional 2D lateral lumbarspine may require a whole body equivalent x-ray dose of about 9-13 mrem,a CT or QCT lateral spine scout scan may require about 3-5 mrem. Becausesuch a lateral scan is taken in any event as a part of a CT or QCTprocedure, its use for vertebral fracture risk assessment and AACestimates does not expose the patient to more radiation if over the samespan of the spine, or may add limited radiation if a greater span of thespine is imaged. A QCT procedure is completed by taking one or more CTslice images in selected planes intersecting selected vertebrae. TheCT/QCT scout view x-ray measurement are computer-processed to identifyand grade vertebral fractures and derive a quantitative assessment ofvertebral fracture risk, and also are computer-processes to identifyaortic calcifications and derive a quantitative assessment ofcardiovascular event risk. The x-ray measurements from CT slices throughone or more vertaebrae (and through the QCT phantom and/or the hip) arecomputer-processed to derive an estimate of bone parameters such as BMD.Preferably, all three assessments (e.g., BMD, vertebral fracture risk,and cardiovascular even risk) are combined in a single report, typicallybut not necessarily together with other information regarding thepatient, such as a graph illustrating the patient's BMD relationship tonormative data for a large population and other information regardingrisk factors and information identifying the patient and the proceduresused to derive the reported data and other information.

A non-limiting example in which DXA rather than QCT or CT is used, anon-limiting method disclosed in this patent comprises using a DXAdevice to obtain x-ray measurements of a patient's anatomy that includesa selected portion of the patient's aorta, wherein the measurements canbe single energy or dual energy and the typically comprise a lateralview of a selected portion of the patient's spine and aorta, derivingdigital image information describing an image of at least the selectedportion of the patient's spine and aorta by computer processing thatuses the x-ray measurements, producing vertebral fracture informationand aortic calcification information describing at least one selectedcalcification property of the selected portion of the aorta by computerprocessing that uses the digital image information, estimating vertebralfracture risk information and cardiovascular risk information indicativeof an assessment of risk of a cardiovascular event by computerprocessing that uses the vertebral fracture and the aortic calcificationinformation, calculating bone assessment information by computerprocessing using the digital image information, and reporting theestimated vertebral fracture risk and cardiovascular risk informationand a record of derived bone assessment information, with or withoutalso reporting other risk factors for the patient, such as cholesterollevels, blood pressure, body fat information, previous cardiovascularevents, etc. In addition to or in place of estimating vertebral boneconditions and fracture risk, DXA measurements of the hip can be used.The report can be shown by displaying it on a computer screen, printingit, storing it in a server or sending it electronically to a remotelocation, and/or otherwise. In the case of using single energy lateralDXA view, the bone assessment can be a vertebral fracture assessment oranother type of morphometry assessment, while in the case of using adual energy lateral view the bone assessment can additionally includebone mineral content or density information, while in the case ofadditionally taking an AP (anterior-posterior or posterior-anterior)view the bone assessment can additionally include information related tobone mineral content or density derived from that view. Reports based onCT and QCT scans and reports based on DXA scans can include the same ordifferent types of assessments and estimates, and a report can includeinformation based in part on each type of scan.

Measurement from different modalities or mixed modalities can be usedfor some or all of the assessments and estimates of interest. Forexample, instead of or in addition to using x-ray measurement obtainedwith a lateral CT or QCT scan, single or dual energy lateral DXA scanscan be used, with measurement similarly processed to derive vertebralfracture risk and cardiovascular event risk. Instead of or in additionto using QCT slice scans to derive bone parameters such as BMD, DXAscans can be used. Instead of or in addition to spine scans for derivingBMD, scans of different anatomy such as the hip can be used, derivedfrom QCT slice scans or DXA scans. The resulting reports can includeinformation derived with the use of different modalities, preferablywith an identification of the modality that produced the reportedinformation. A risk assessment quantification or a BMD estimate can bebased on information from a single modality or on a combination ofinformation from two to even more modalities.

A non-limiting example of a system disclosed in this patent applicationcomprises a dual x-ray energy bone densitometer that obtains x-raymeasurements of a patient's anatomy that includes a selected portion ofthe patient's spine and aorta, and/or of another suitable part of thepatient's anatomy such as the hip. Alternatively or in addition, thesystem comprises a CT scanner preferably equipped with QCT hardwareand/or software. Preferably the patient is scanned in a generallylateral view, e.g. a supine patient is scanned from the side. If boneparameters such as BMD are desired and a QCT device is used, the patientalso is scanned for CT slice images, as common for QCT estimates of BMD.If a DXA device is used, the x-ray measurements can be at a singleenergy or dual energy and typically come from a lateral view of thepatient although hip measurements may come from an AP view. A computeris coupled with the DXA device or the CT/QCT device top the lateral viewx-ray measurements and process them to derive digital image informationdescribing an image of at least the selected portion of the patient'sspine and aorta and/or other anatomy. The computer is further programmedto process the lateral view digital image information to producevertebral fracture and aortic calcification information describing atleast one selected calcification property of the selected portion of theaorta, and is further programmed to process the aortic calcificationinformation to estimate cardiovascular risk information indicative of anassessment of risk of a cardiovascular event for the patient and toprocess the vertebral fracture information to estimate vertebralfracture risk information indicative of an assessment of the risk to thepatient of a future vertebral fracture. The computer is still furtherprogrammed to process x-ray measurements obtained from QCT slice imagesand/or dual energy DXA measurements of the spine, hip and/or otheranatomy to estimate one or more bone parameters such as BMD and/orstructural information regarding the hip or other anatomy. The systemfurther includes a reporting unit such as a display coupled with thecomputer to receive the vertebral fracture risk information and thecardiovascular risk information and show it on a screen and/or otherwisereport it. A further non-limiting example is a computer program productthat can be loaded as an application program in a computer to carry outexamples of the disclosed method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in block diagram form one example of the maincomponents of a system that estimates and reports risk of vertebralfracture and of cardiovascular events and bone parameters such as BMDusing dual x-ray energy bone densitometry (DXA) data and/or QCT.

FIG. 2 a illustrates a prior art DXA scanning systems that can generateand process DXA measurements when programmed to carry out the processdisclosed in this patent specification.

FIG. 2 b illustrates a prior art QCT scanning systems that can generateand process x-ray measurements when programmed to carry out the processdisclosed in this patent specification.

FIG. 3 illustrates a single energy lateral DXA image showing spinalfracture and aortic calcification in the lumbar aorta; a QCT laterallocalization or scout image can be similar.

FIG. 4 illustrates a non-limiting example of a display of vertebralfracture risk and cardiovascular risk information and bone conditioninformation that can be derived according to the disclosure herein atleast in part from DXA and or CT/QCT x-ray measurements.

FIG. 5 illustrates process components of a method for generating resultssuch as those in FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, the main components of a system carrying out oneexample of the disclosed method of estimating and reporting a risk ofvertebral fracture and cardiovascular events as well as bone parameterssuch as BMD, are a dual x-ray energy bone densitometer 10 and/or aCT/QCT system 11, a processing workstation 12, and a reporting station14. Densitometer 10 can be the scanning and pre-processing part of adevice such as disclosed in U.S. Pat. No. 6,385,283, or the densitometeravailable from Hologic, Inc. under the trade name Discovery and equippedwith appropriate software including CADfx and IVA software. Its purposehere is to obtain x-ray measurements of patient's anatomy that includesthe appropriate part of the spine and aorta, for example the portion ofthe abdominal aorta anterior to the lumbar spine. QCT system 11 can be aconventional CT system equipped with known QCT hardware and software(including a QCT phantom) and adapted to provide x-ray measurementsoutput to work station 12 for further processing according to the methoddisclosed in the patent specification. When densitometer 10 uses anx-ray beam alternating between high and low energies, as in theDiscovery system, the x-ray measurements used in this example can besingle energy measurements for a lateral view. As noted above, in thealternative single energy images can be extracted from dual energymeasurements. Single energy x-ray measurements from DXA can also be usedfor bone assessment such as CADfx, IVA, or vertebral fractureassessment. In the alternative, the x-ray measurements can be dualenergy measurements, obtained with DXA equipment 10 with an x-ray beamalternating between two energies or with a scanning densitometer thatuses an x-ray beam with a wider energy range and two sets of detectors,or with another type of densitometer. When dual energy measurements areavailable, they can be used for additional or alternative boneassessment information, such as information regarding bone mineralcontent or density. The x-ray measurements for vertebral fractureassessment and AAC typically are acquired from a lateral view of thepatient, while those for additional or alternative bone assessment canbe acquired in a lateral or other views such as an AP view.

After conventional initial pre-processing, the x-ray measurements aredelivered to workstation 12 that has one or more computers programmed tocarry out known processing to derive digital image information such as,but not limited to, pixel values for a lateral image from CT/QCT system11 or for a lateral DXA single-energy and/or dual-energy image of thepatient's anatomy. One example of a workstation with functionalitysuitable for assessing vertebral fracture risk using DXA outputs isdisclosed in said U.S. Pat. No. 6,385,283. Another example is theworkstation of the Discovery system when equipped with said CADfx andIVA options. Instead of or in addition to so processing DXA outputs,workstation 12 can similarly process the lateral view CT/QCT outputs tosimilarly derive estimates of vertebral fracture risk. In addition,workstation 12 processes the outputs of DXA system 10 in a conventionalmanner to derive estimates of bone parameters such as BMD, and/orprocesses the CT slice view outputs from QCT system 11 in a manner knownin QCT technology to derive similar bone condition parameters such asBMD. In addition, workstation 12 is programmed to carry out new steps inwhich it processes the digital image information for a lateral view fromDXA system 10 and/or CT/QCT system 11 to produce aortic calcificationinformation regarding a selected portion of the patient's aorta, and isprogrammed to use the result to estimate cardiovascular riskinformation. The output of workstation 12 is delivered to reportingstation 14 that can include one or more computer screens for displayingthe results from workstation 12, printing equipment, magnetic andoptical disc drives or other drives for longer term storage of thoseresults and other data, communication facilities to transfer the resultsand other data to remote locations and storage such as PACS, etc.

FIG. 2 a illustrates in greater detail a known x-ray bone densitometersystem with facilities that can be used to practice the methodsdisclosed in this patent specification. It includes a scanning system 30that comprises a patient table unit 32 with a patient table 50 and aC-arm 56 serving as a source-detector support. A workstation 34 controlspatient table unit 32 and C-arm 56 and processes scan data intoquantitative bone assessment information such as BMD, into images, andinto IVA and vertebral risk assessment information. Workstation 34includes a power supply module 36, one or more host computers 38 with amass data storage devices 40, an operator console keyboard 42, a displaymonitor 44 and a printer 46. Table 50 can move up and down and along itslong dimension and may also move along its short dimension. C-arm 56also moves along the length of table 50 to scan a patient thereon with afan-shaped beam of x-rays from source 52 so that a detector array 54 andassociated electronics can produce dual energy or single energy scandata. The C-arm may also be able to move across the table. For thepurposes of carrying out the methods disclosed in this patentspecification, different densitometry systems can be used so long asthey can do a lateral scan of a patient and obtain the requisite singleenergy and/or dual energy x-ray measurements of the appropriate aorticportion. They can range from a basic model in which the C-arm does notrotate so that the lateral scan needs to be done in the decubitusposition, and the table has limited range or motions or no motion, tothe most sophisticated models that have many more features and in whichthe lateral scan can be done either in the supine or in the decubituspositions. One of the features that some of the known x-ray bonedensitometry systems have is software that either completelyautomatically or with some operator input identifies specified RegionsOf Interest (ROI) such as vertebral bodies or other bone structures suchas the femur head. See, for example, CADfx and U.S. Pat. Nos. 5,850,836and 5,228,068 that pertain to morphometry processes that identifyvertebral bodies and U.S. Pat. No. 6,853,741 that pertains mainly to thefemur head. Morphometry options and CADfx and IVA options have beenavailable from Hologic, Inc. for its x-ray bone densitometers.

When used for carrying out a method disclosed in this patentapplication, units 2, 32, 50, 52, 54, and 56 of FIG. 2 can serve as anexample of densitometer 10 of FIG. 1; units 34, 36, 38, 40 and 42 canserve as and example of workstation 12 of FIG. 1; and units 40 and 46can serve as an example of reporting station 14 of FIG. 1.

FIG. 2 b schematically illustrates a QCT system that comprises a gantry60 that carries an x-ray source emitting a fan-shaped x-ray beam that isdetected at x-ray detector assembly 68 after passing through an axialslice 70 of a patient and a QCT phantom 72 supported on a patient bed74. In operation in this example, first the source and detectors 62 and68 are rotated approximately 90° around the patient from the positionsshown in FIG. 2 b and patient bed 74 moves axially, along the length ofthe patient, relative to gantry 60 while x-ray beam 64 is ON to therebytake a lateral localization or scout x-ray image of the desired anatomy.After selection of the appropriate vertebrae and gantry tilt, gantry 60rotates around the patient in one or more selected planes to take CTslice images. The illustration pertains to third generation CT geometrybut other geometries can also be used for similar purposes. Knowncontrols and electronics pre-process the x-ray measurements fromdetector assembly 68 for delivery to work station 12.

FIG. 3 illustrates a single energy lateral image from a dual x-rayenergy densitometer, but a lateral localization or scout image from aCT/QCT system is similar. AAC can be seen anterior of lumbar vertebraeL2 and L3. Various parameters of this AAC can be detected with computerassistance such as its length along the aorta either in absolute unitsor in units scaled to the height of the laterally adjacent vertebralbodies, its area in the image, its bone mineral content (BMC) in unitssuch as those commonly used in DXA, it a real density of calcification,or other parameters related to the degree and nature of the detectedcalcification. While FIG. 3 illustrates a single energy image, dualenergy images can be used instead or in addition to detect and assessAAC parameters that may be comparably or better visualized in dualenergy imaging, and a CT/QCT lateral localization or scout scan can beused instead of or in addition to a DXA scan. The lines throughinter-vertebral spaces in FIG. 3 delineate lumbar vertebrae. It isimportant that DXA or localization/scout lateral images such as that inFIG. 3, which typically are produced as a part of a QCT procedure buttypically cover a shorter span of the spine, or when using the IVAprocedure, show the thoracic region as well as the lumbar region in asingle image, which it typically not the case with conventionalradiographs. Accordingly, the same CT/QCT lateral image or DXA image canbe used to detect and assess thoracic vertebral fracture over a greaterspan of the spine and thoracic arterial calcification (TAC) in additionto or instead of abdominal arterial calcification and the resultinginformation can be used in assessing and reporting risk of vertebralfracture and cardiovascular events.¹¹

The detection of AAC and/or TAC from lateral CT/QCT images or DXA imagescan be through a computer assisted process that is entirely automated orinvolves some participation by the health care professional. In anentirely automated process, a computer search algorithm evaluates theimage information, for example by testing pixel values of a pixel-basedimage to identify pixel clusters that match criteria indicative ofaortic calcification. Because calcification can be somewhat patchy, thealgorithm can be made to add up clusters that individually suggestcalcification but are not contiguous. Constraints can be imposed on suchadding up, such as requirements that the clusters have minimum size,that they be within a specified area, that they be spaced by no morethan a specified distance, etc. The search algorithm can first identifythe vertebral bodies, for example using the commercially available CADfxsoftware from Hologic, Inc., and then search an ROI that is preset toencompass a specified area relative to the vertebral bodies in theimage, for example an area within a specified distance anterior from thelumbar and/or thoracic vertebrae in a lateral view. The distance can beexpressed as absolute units or in units of vertebral size for theparticular patient. Various search algorithms can be used; as anon-limiting example an algorithm may select as AAC pixels those thathave pixel values exceeding a threshold and possibly meeting additionalcriteria such as comparison with adjacent pixels or with a thresholdderived from a histogram of pixels in a specified ROI. As a non-limitingexample, the threshold can be based on an average of all pixels in thesearched ROI or on a histological value related to pixel values in theROI or in other regions of the image. More sophisticated searchalgorithms can be used as an alternative, using techniques such as thosediscussed in U.S. Pat. No. 6,138,045 and the patents cited at column 1,lines 25-40 thereof, which also are incorporated by reference herein. Asyet another alternative, image marking by a health professional canassist in the computer identification of the ROI to be searched. Forexample, by using a mouse of another input device, the healthprofessional can mark the image such as by drawing an outline around therelevant portion of the aorta, or by marking the vertical ends of theAAC visible in the image, or by outlining the AAC, or in some other way,and the search algorithm can then use the marking information to selectthe ROI and/or to otherwise use the marking information in identifyingAAC parameters. As yet another alternative, the function of the searchalgorithm can be limited to calculating the distance between marksdesignating the vertical ends of the AAC portion, or to calculating theAAC area outlined by the health professional. As noted above, the resultof this process is aortic calcification information that can include oneor more parameters such as the length of the calcified portion inappropriate units along the length of the pertinent aortic portion, thearea of calcification, the BMC of the calcification, the a real densityof the calcification (BMC/area of calcification), and possible otherparameters. Parameters such as the amount of calcification arecalculated using dual energy image information rather than a singleenergy image, in the manner currently used in commercial dual x-rayenergy bone densitometers, and in units such as grams of calciumhydroxyapetite equivalent. In addition, calcification informationderived from QCT slice views as in said published U.S. patentapplication can be used to estimate local calcification and/or asinformation serving for calibration of calcification informationestimated based on lateral images. Both the total amount of aorticcalcification and the area and/or length of the calcification can bepredictive of disease and its severity and can be used in arterialcalcification grading schemes, for example schemes such as thoseproposed in the cited articles. The aortic calcification informationcalculated or estimated in this manner can be presented as digital dataquantifying the estimates and/or by way of grading results, for example5 grades or 8 grades or some other number of grades indicative of thedegree and/or nature of calcification and based on the estimatedparameters alone or in combination with other factors such as clinicalinformation regarding the patient and possibly input from a healthprofessional.

Arterial calcification information derived in this manner is used as aninput to a computer assisted process in workstation 12 that calculatesor estimates cardiovascular risk information, possibly also based onadditional factors such as clinical data input by a health professionalor available from another source and possibly other data such asnormative data for patient populations relevant to the patient beingexamined. In a simplified example, if a numerical scoring system of 8grades is used in the assessment of arterial calcification, each gradecan be related through a look-up table to a respective grade of risk ofcardiovascular event or to a probability of such event in a specifiedtime period. The look-up table can be based on current knowledge of suchrelationship or on normative data derived in known manner from examininga historical base of images showing arterial calcification and relatingthem to actual occurrence of cardiovascular events in the patientpopulation. Additional or alternative statistical studies and approachescan be used in creating and refining the look-up table. Such techniqueshave been used in creating, for example, the ATP III GuidelinesAt-A-Glance Quick Desk Reference available from the National Instituteof Health, National Heart, Ling and Blood Institute, that relates a setof factors such as cholesterol level, cigarette smoking, hypertensionand others to level of coronary heart disease (CHD). The arterialcalcification information can be one of the factors that go into the CHDguidelines, hereby incorporated by reference. Alternatively, thearterial information can be used by itself to produce cardiovascularrisk information such as, but not limited to, a numerical or otherwisequantified grade of risk. Still alternatively, the arterialcalcification information can be used to estimate cardiovascular riskinformation when combined with clinical information regarding the patentand/or other information entered into the process by a healthprofessional or available from another source, to estimate riskinformation in a manner similar to that in said guidelines. Thecardiovascular risk information can then be used to help the healthprofessional assess and treat the patient, and can additionally be usedas an entry to a process that automatically produces recommendedtreatment choices, again in the manner done in said guidelines. The termcardiovascular risk information is used in this patent specification ina broad sense, and can be a score such as in the CHD Guidelines or toother information that pertains to risk associated with the patient'scardiovascular system.

The risk information and if desired the arterial calcificationinformation and other information can be reported in any number of ways.As a non-limiting example, it can be added to a report such asillustrated in FIG. 2 or FIG. 3 of said U.S. Pat. No. 6,385,283. Oneexample of such combined report is illustrated in FIG. 4 in this patentspecification, which contains all of the information illustrated in FIG.3 in the patent and, additionally, illustrates an image of an artery 118that has a calcified portion 118 a and adds cardiovascular risk relatedinformation 120. FIG. 4 is a drawing rather than an actual DXA image (asis FIG. 3 herein) or an actual CT/QCT lateral localization or scoutimage. As seen in FIG. 4, information 120 comprises an entry “AAC score4” that indicates the degree and nature of detected arterialcalcification according to an example of a grading scheme, an entry “CVrisk score 15” that indicated the cardiovascular risk grade according toan example of another grading scheme, and an entry “Guideline 5”referring to an example of a treatment guideline that relates thepatient's CV risk score to a suggested treatment or choice of treatmentsaccording to a guideline similar in principle to said NIH guideline. Ofcourse, this is only an illustrative example of entries 120, and more orless information related to AAC and cardiovascular risk can bedisplayed. As an alternative, some or all of the information such asthat displayed at 120 can be displayed by itself, without some or all ofthe other information seen in FIG. 4. In such case, information such asat 120 can be displayed alone (or with image 106) by itself on acomputer screen, and possibly but not necessarily concurrently with aseparate display of bone assessment information such as that seen inFIG. 4. In addition, the report can include and selectively displayother reported information 122, for example clinical information aboutthe patient such as cholesterol levels, information regarding previouscardiovascular events, regarding blood pressure, weight and height, etc.FIG. 4 also illustrates an example of display of vertebral fractureinformation at 114 and vertebral fracture risk information at 116, andbone conditions information such as BMC and BMD at 104. FIG. 4 alsoillustrates additional material such as data identifying the patient,the time and type of scan, the equipment used, etc. The dates arearbitrary and do not in this case correspond to when the resultsillustrated in FIG. 4 were actually derived. If displayed results wereobtained from CT/QCT devices, an appropriate indication of the source ofthe basic information would be added, although in this case onlymeasurements from a DXA device were used.

FIG. 5 illustrates an example of main components of a process accordingto the disclosure above. Process component 500 is a DXA procedure thatobtains single energy and/or dual energy x-ray measurements of apatient's anatomy that includes a selected portion of a patient's aorta,preferably in a lateral view and if desired in an AP view as well.Component 500 can carry out conventional pre-processing of the x-raymeasurements, or can deliver raw measurements. Process component 501 isa CT/QCT procedure that obtains a generally lateral localization orscout view of a desired span of the spine and aorta, and then QCT sliceviews, and can carry out conventional pre-processing of the x-raymeasurements to prepare them for use in the next process component.Process component 502 receives the x-ray measurement information fromcomponent 500 and/or from component 501 in digital form, typically inthe form of information describing the value and position of each imagepixel for the single energy or for each of two x-ray energies in thecase of information from component 500 and in the form of image pixelvalues for the lateral image and the one or more QCT slice images in thecase of information from component 501, applies any necessaryconventional pre-processing thereto, such as dark current correction andother corrections, and derives digital image information that describesan image of at least the pertinent portion of the spine and aorta in agenerally lateral view, as in FIG. 4, and/or digital image informationdescribing QCT slice images. The image information can be in the form ofpixel data containing a pixel value for each respective pixel of asingle energy image and/or the processed dual energy image thateffectively eliminates soft tissue but leaves bone and calcification inthe image, or in the form of similar information for a CT/QCT lateralview and QCT slice views. The images in this case can be the same asavailable in conventional DXA and/or IVA or CT or QCT or they can beoptimized for visualizing and/or detecting arterial calcification usingknown techniques. Process component 506 uses the output of component 504in the manner known in conventional DXA and/or QCT to generate boneassessment information such as BMD and/or IVA and to provide it to oneor more reporting components 512. Process component 508 is unique to theprocess disclosed in this patent specification and receives imageinformation from component 504 to process it according to the principlesdiscussed above to thereby produce aortic calcification information. Asdiscussed above, in a simplified example the output of process component508 can be only a grade of calcification, but alternatively it caninclude additional and more detailed digital information definingarterial calcification parameters such as a measure of the verticalextent of calcification, area of calcification, etc. Process component510 uses the arterial calcification information from component 508 in acomputer assisted process that estimates cardiovascular riskinformation, for example a patient's risk of a cardiovascular event,according to the principles discussed above. The estimate can be basedsolely on the arterial calcification information from component 508 orit can additionally use traditional clinical information that processcomponent 509 provides. The clinical information can be patient age andother patient information of the type that goes into the processoutlined in said NIH guidelines, and/or it can include additionalclinical observations of a health care professional applicable topatient being examined. The output of process component 510 goes to oneor more reporting components 512. A reporting component 512 can displaythe appropriate information, can store it for future use, direct it to aremote location, print it, or otherwise utilize it. A reportingcomponent 512 can display or otherwise utilize only bone assessmentinformation, or only cardiovascular risk information, or only vertebralfracture risk information, or only other information, or any desiredcombination of sub-combination thereof. In addition, process component510 can generate recommended treatment information and supply it to oneor more reporting components 512 for display or other use.

There exist 10-year cardiovascular risk scores, for example theFramingham Point Score or PROCAM¹³ risk score. These measure clinicalrisk factors for cardiovascular risk. Since AAC is independent of theserisk factors, the additional risk from AAC grade/score can be used tomore accurately calculate an individual's risk. For example, thecomputer can calculate the Framingham Point Score from inputs (age,total cholesterol, HDL, Systolic BP, gender) or the Framingham Pointscore could be directly entered for the patient. The computer cancombine this risk score with the additional relative risk conferred bythe AAC grade/score to obtain a 10 year risk that more accuratelyreflects the individual's risk. This is useful because various treatmentguidelines(http://www.nhlbi.nih.gov/guidelines/cholesterol/atglance.pdf) areavailable that depend on the individuals 10 year cardiovascular riskscore. The treatment guidelines for the level of risk calculated canalso be included in the report.

The specific examples described above will suggests to persons skilledin the relevant technology variations thereof and are not intended asthe only examples of the inventions to which the claims below aredirected. The claims are intended to encompass such variations.

CITATIONS TO MATERIAL INCORPORATED BY REFERENCE IN THIS PATENTSPECIFICATION

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1. A computer-implemented method of estimating cardiovascular riskinformation for a patient using aortic calcification informationobtained with a dual x-ray energy bone densitometer or a CT/QCTlocalization or scout scan and generating a record of the estimated risktogether with a record of bone assessment information, comprising:obtaining x-ray measurements of a patient's anatomy that includes aselected elongated portion of the patient's aorta, by using a dualenergy bone densitometer or a CT/QCT localization or scout scan thatselectively generates at least one of single energy range measurementsand dual energy range measurements; deriving digital image informationdescribing an image of at least the selected portion of the patient'saorta, by computer processing that uses said x-ray measurements;producing aortic calcification information describing at least oneselected calcification property of the selected portion of the aorta, bycomputer processing that uses the digital image information; estimatingcardiovascular risk information related to an assessment of risk of acardiovascular event by computer processing that uses the aorticcalcification information; calculating first bone assessmentinformation, by computer processing that uses the digital imageinformation; and reporting the estimated cardiovascular risk informationand the calculated bone assessment information.
 2. A method as in claim1 including inputting additional information regarding clinical riskfactors for the patient and using said additional information in saidestimating of cardiovascular risk information.
 3. A method as in claim 1including showing an image of the patient's anatomy derived using saiddigital image information, together with the cardiovascular riskassessment and bone assessment information.
 4. A method as in claim 1 inwhich the calcification information comprises a grade calculatedaccording to a selected grading scheme.
 5. A method as in claim 1 inwhich calcification property is at least one of length of a calcifiedportion of the aorta, area of the calcified portion, mineral content ofthe calcified portion, and mineral content per unit area of thecalcified portion.
 6. A method as in claim 1 in which said reportingcomprises concurrently showing the cardiovascular risk information andthe bone assessment information.
 7. A method as in claim 1 in which saidreporting comprises showing the cardiovascular risk information and thebone assessment information at different times.
 8. A method as in claim1 in which said reporting comprises showing the cardiovascular riskinformation and the bone assessment information at a single display ordocument.
 9. A method as in claim 1 in which said reporting comprisesshowing the cardiovascular risk information and the bone assessmentinformation at separate display screens or documents.
 10. A method as inclaim 1 in which the producing comprises scaling aortic calcificationinformation to patient's vertebral size information.
 11. A method as inclaim 1 in which the x-ray measurements are single energy range x-raymeasurements.
 12. A method as in claim 1 in which the x-ray measurementsare dual energy range x-ray measurements.
 13. A method as in claim 1 inwhich the x-ray measurements comprise a localization or scout scan imagetaken with a CT/QCT system.
 14. A method as in claim 1 in which theobtaining comprises obtaining the x-ray measurements from a lateral viewof the patient.
 15. A method as in claim 13 the deriving comprisesprocessing a lateral view measurements, and further including obtainingdual energy range AP x-ray measurements from an AP view of the patientand computer processing the AP measurements to derive and report secondbone assessment results that include indications of BMD and/or BMC. 16.A method as in claim 15 in which the lateral x-ray measurements aresingle energy range x-ray measurements.
 17. A method as in claim 1 inwhich the selected portion of the aorta comprises a selected portion ofthe abdominal aorta.
 18. A method as in claim 1 in which the selectedportion of the aorta comprises a selected portion of the thoracic aorta.19. A computer-implemented method comprising: obtaining x-raymeasurements of a patient's anatomy that includes a selected elongatedportion of the patient's aorta, by using a dual x-ray energy bonedensitometer system or a CT/QCT localization or scout scan; using thex-ray measurements to derive digital image information describing animage of at least the selected elongated portion of the patient's aorta;producing aortic calcification information describing at least oneselected calcification property of the selected portion of the aorta, bycomputer processing that uses the digital image information; estimatingcardiovascular risk information related to an assessment of risk of acardiovascular event by computer processing using the aorticcalcification information; and reporting the calculated cardiovascularrisk information.
 20. A method as in claim 19 in which the digital imageinformation describes values of image pixels, and the producing ofaortic calcification information comprises applying at least oneselected computer search algorithm to the digital image information toidentify pixel groupings that meet selected pixel value characteristics.21. A method as in claim 20 including displaying an image of thepatient's anatomy, including an image of the selected portion of theaorta, derived from said digital image information, and manually markinga calcified portion of the aorta visible in the image, wherein theproducing of aortic calcification information comprises usinginformation regarding said marking in the course of computer processingthe image information.
 22. A method as in claim 19 including displayingan image of the patient's anatomy, including an image of the selectedportion of the aorta, derived from said digital image information, andmanually marking a calcified portion of the aorta visible in the image,wherein the producing of aortic calcification information comprisesusing information regarding said marking in the course of computerprocessing the image information.
 23. A method as in claim 19 in whichthe producing of aortic calcification information comprises treating ascalcified a composite of non-contiguous parts of the aorta that meetselected criteria.
 24. A method as in claim 19 in which said x-raymeasurements are single energy x-ray measurements.
 25. A method as inclaim 19 in which said x-ray measurements are dual energy x-raymeasurements.
 26. A method as in claim 19 in which said x-raymeasurement are derived by a lateral CT/QCT localization or scout scan.27. A method as in claim 19 including inputting additional informationregarding clinical risk factors for the patient and using saidadditional information in said estimating of cardiovascular riskinformation.
 28. A method as in claim 19 including deriving boneassessment information by computer processing that uses said x-raymeasurements, and wherein the reporting comprises showing thecardiovascular assessment information and the bone information.
 29. Amethod as in claim 28 in which the reporting comprises showing thecardiovascular risk information and the bone assessment information atdifferent displays or documents.
 30. A method as in claim 28 in whichthe reporting comprises showing the cardiovascular risk information andthe bone assessment information concurrently.
 31. A method as in claim30 in which the reporting comprises showing the cardiovascular riskinformation and the bone assessment information at same display ordocument.
 32. A method as in claim 19 including displaying informationrelated to treatment guidelines related to the cardiovascular riskinformation.
 33. A method as in claim 19 in which the obtaining of x-raymeasurements comprises scanning the patient with a fan beam of x-rays.34. A method as in claim 19 in which the obtaining of x-ray measurementscomprises scanning the patient with a single energy fan beam of x-rays.35. A system comprising: an acquisition device comprising at least oneof a dual x-ray energy bone densitometer that selectively obtains singleenergy or dual energy x-ray measurements of a patient's anatomy thatincludes a selected elongated span of the patient's aorta and a CT/QCTunit that selectively obtains localization or scout x-ray measurementsof a patient's anatomy that includes a selected elongated span of theaorta; a computer coupled with at least one of the densitometer and theCT/QCT unit and receiving said x-ray measurements therefrom, saidcomputer being programmed to: (a) process the x-ray measurements andthereby derive digital image information describing an image of at leastthe selected portion of the patient's aorta, (b) process the digitalimage information and thereby produce aortic calcification informationdescribing at least one selected calcification property of the selectedportion of the aorta, and (c) process the aortic calcificationinformation and thereby estimate cardiovascular risk information relatedto an assessment of risk of a cardiovascular event for the patient; anda display coupled with the computer and receiving said cardiovascularrisk information therefrom and displaying an indication of acardiovascular risk for the patient.
 36. A system as in claim 35 whereinsaid computer is further programmed to process the digital imageinformation from the densitometer and thereby calculate bone assessmentinformation for the patient.
 37. A system as in claim 35 wherein saidCT/QCT unit provides QCT slice image digital information and saidcomputer is further programmed to process the slice image digital imageinformation and thereby calculate bone assessment information for thepatient.
 38. A system as in claim 37 wherein said display is coupledwith said computer to receive the bone assessment information therefromand displays an indication of the bone assessment information.
 39. Asystem as in claim 37 in which said bone assessment informationcomprises bone fracture risk information.
 40. A system as in claim 36 inwhich said x-ray measurements comprise dual energy measurements and saidbone assessment information comprises information related to at leastone of bone mineral content and bone mineral density.
 41. A system as inclaim 40 in which said bone assessment information comprises bonefracture risk information.
 42. A system as in claim 41 in which thex-ray measurements comprise single energy measurements and said bonefracture risk information is based on the single energy measurements.43. A system as in claim 36 in which said digital image data comprisespixel values for respective pixels of a two-dimensional image of thepatient's anatomy, and wherein said computer is programmed to carry outat least one pixel-based search algorithm in a process producing saidaortic calcification information.
 44. A system as in claim 36 in whichsaid densitometer comprises a source of a fan-shaped beam of x-rays anda detector for x-rays traveling within respective sectors of said fanbeam.
 45. A computer readable medium storing program information forcarrying out one or more sequences of instructions wherein execution ofthe instructions by one or more processors causes the one or moreprocessors to perform the steps of: receiving at least one of singleenergy x-ray measurements or dual energy x-ray measurements and lateralCT/QCT localization or scout view of a patient's anatomy that includes aselected elongated portion of the patient's aorta; processing the x-raymeasurements to derive digital image information describing an image ofat least the selected portion of the patient's aorta, processing thedigital image information to produce aortic calcification informationdescribing at least one selected calcification property of the selectedportion of the aorta, processing the aortic calcification information toestimate cardiovascular risk information related to an assessment ofrisk of a cardiovascular event for the patient; and displaying anindication of the estimated cardiovascular risk for the patient.
 46. Acomputer readable medium as in claim 45 in which said x-ray measurementsare single energy measurements taken in a lateral view of the patient.47. A computer readable medium as in claim 45 in which said x-raymeasurements are dual energy measurements taken in a lateral view of thepatient.
 48. A computer readable medium as in claim 45 in which saidx-ray measurements are obtained with a CT/QCT unit.
 49. A computerreadable medium as in claim 45 in which said processing furthercomprises using said x-ray measurements to derive bone assessmentinformation and said displaying further comprises displaying the boneassessment information.
 50. A computer readable medium as in claim 49 inwhich said bone assessment information comprises bone fracture riskassessment information.
 51. A computer readable medium as in claim 49 inwhich said x-ray measurements comprise dual energy measurements and saidbone assessment information comprises information related to at leastone of bone mineral content and bone mineral density.
 52. A computerreadable medium as in claim 49 in which said digital image datacomprises pixel values for respective pixels of a two-dimensional imageof the patient's anatomy, and said processing comprises applying atleast one pixel-based search algorithm in a process producing saidaortic calcification information.
 53. A method of using a QuantitativeComputed Tomographt (QST) scanner system to derive and display each ofnumerical bone mineral density (BMD) data for the patient, a lateralimage of at least a majority of both the lumbar and thoracic vertebraeof the patient, and future bone fracture risk data for the patient,comprising: using the QCT scanner to scan a patient with x-rays andgenerate both (a) numerical bone mineral density (BMD) data for thepatient and (b) a lateral projection x-ray image of at least a majorityof both the lumbar and thoracic vertebrae of the patient; providingcurrent fracture data relating to the presence or absence of vertebralfractures or deformities in the image; computer-processing the BMD dataand the current fracture data to produce future bone fracture datataking into account both the BMD data and the current fracture data; anddisplaying a report showing the numeric BMD data, the image, and thefuture bone fracture risk data.